Test Your Tech A spread sheet: A. Only happens on laundry day. B. Is covered with food during holiday meals. C. Helps answer "what-if" questions. 1 D.A. Clements, UW Information School5/26/2016

Test Your Tech A spread sheet: A. Only happens on laundry day. B. Is covered with food during holiday meals. C. Helps answer "what-if" questions. 2 D.A. Clements, UW Information School5/26/2016

Announcement Software for rest of quarter Microsoft Excel in Lab 10 Microsoft Access for the rest of the labs and Project 3 Microsoft Access—PC's only Mac users will have to use the labs on campus No Mac equivalent D.A. Clements, UW Information School 3 5/26/2016

Announcements Free copy of Access, Windows 7, etc., for educational/academic use: Links on Computing page on Course Web site Search for CSE or INFO to find the link on the page Username is your full UW address Password is different! Click on "send a reminder" Check wherever your forwards to 4 D.A. Clements, UW Information School5/26/2016

Announcements Readings Today—Ch 15 Wednesday—Ch 16 D.A. Clements, UW Information School 5 5/26/2016

Announcements Project 2B due Wednesday night at 10pm Drop-In Labs Tuesday 8:30am MGH 430 Tuesday 5pm MGH 430 Wednesday CLUE Tutoring 7pm MGH pts extra credit per CLUE session 5/26/2016D.A. Clements, UW Information School 6

Announcements Lab 10 due Friday night at 10pm Drop-In Labs Thursday 8:30am MGH 430 Friday 1:30pm MGH 430 5/26/2016D.A. Clements, UW Information School 7

Announcements Tight deadlines for rest of course No extensions No lab time scheduled for Project 3A 5/26/2016D.A. Clements, UW Information School 8

Unit III: Data Storage, Transfer, and Retrieval Keeping your private information private and secure FIT 100–Fluency with Information Technology D.A. Clements 9 D.A. Clements, UW Information School 5/26/2016

Where we've been... Unit I—Connections Hardware, networks, protocols, Internet, Web, building Web pages Unit II—Programming Concepts common to all programming languages Unit III—Data Storage, retrieval, transfer 5/26/2016D.A. Clements, UW Information School 10

Unit III: Data Storage Format—physical and logical Retrieval The information you need when you need it Transfer Between people, departments, organizations Media—spreadsheets, databases, XML 11 D.A. Clements, UW Information School5/26/2016

Spreadsheets Spreadsheets are a powerful abstraction for organizing data and computation 12 D.A. Clements, UW Information School 5/26/2016

An Array of Cells A spreadsheet is a 2-dimensional array of cells…it’s 3D with multiple worksheets Rows or columns represent a single data type They will be operated on similarly, so that’s easy to do Adding more data of the same type means adding more rows or columns Often spreadsheets contain numbers, but text- only spreadsheets are useful, too 13 D.A. Clements, UW Information School5/26/2016

Looking for Similar Ideas Spreadsheets are not so unusual The position (row/column) names the data, as with memory locations, variables, forms, etc. Operating on all elements of a column (or row) is an iteration, though not the World Famous Iteration Setting a cell to a formula is an (unevaluated) assignment statement with cells as variables The formula is an expression Functions are built-in expressions Think of spreadsheets as a handier interface for calculating than JavaScript 14 D.A. Clements, UW Information School5/26/2016

Familiar Terminology column heading row name cell 15 D.A. Clements, UW Information School5/26/2016

Familiar Terminology column heading row name cell 16 D.A. Clements, UW Information School5/26/2016

Familiar Terminology column heading row name cell formula column name referenced cell E2 17 D.A. Clements, UW Information School5/26/2016

Familiar Terminology formula column name referenced cell E2 18 D.A. Clements, UW Information School5/26/2016

Formulas The data in a spreadsheet can be manipulated using formulas The value in D2 (selected cell) is the value in B2 times 0.621…the result is shown but the cell has the formula. 19 D.A. Clements, UW Information School5/26/2016

Apply Formula Again The data in a spreadsheet can be manipulated using formulas Notice the formula. 20 D.A. Clements, UW Information School5/26/2016

Filling Replicates Formulas Fill is a spreadsheet shortcut for copy- and-paste. It’s magic! Grab the fill tab and pull in the direction to be pasted. Fill tab 21 D.A. Clements, UW Information School5/26/2016

Relative & Absolute Addressing References to cells happens in two ways: Relative and Absolute (with $) F2relative column, relative row F$2relative column, absolute row $F2absolute column, relative row $F$2absolute column, absolute row Relative references change when pasted/filled; absolute references do not! Your intent determines which to pick. 22 D.A. Clements, UW Information School5/26/2016

A Powerful Translation The graphic shows the equations in the cells with the translation: The row changes going down but the column doesn’t. 23 D.A. Clements, UW Information School5/26/2016

An Example Creating a discount table uses both relative and absolute refs Consider store credit of $1 per $10 spent $3 store credit for every 2 CDs (1 earns $1) A cell is based on first column, top row data in that row and column…must mix relative and absolute references 24 D.A. Clements, UW Information School5/26/2016

Series Another handy property of fill is that it can make a series based on constants Fill Sunday => Monday, Tuesday, Wed… Fill 22 Feb => 23 Feb, 24 Feb, 25 Feb… More generally Series fill will even count using a constant Counting by odd sizes: give 1 st two items 25 D.A. Clements, UW Information School5/26/2016

SPREADSHEET VS. DATABASE Excel vs. Access… 5/26/2016D.A. Clements, UW Information School 26

Tables 5/26/2016D.A. Clements, UW Information School 27 Word Table Excel Table Access

Advantages of Spreadsheets Familiar format of rows and columns Can work directly with the data "What-If" scenarios Involved computations like taxes Storing lists D.A. Clements, UW Information School 28 5/26/2016

Microsoft reports that…. 70% of Excel users use it like a database D.A. Clements, UW Information School 29 5/26/2016

Databases are better… When you… Have a lot of spreadsheets Need to pass data back and forth between spreadsheets Scroll a lot to find answers Have a lot of repetitious data, like Many contacts at same company with Repeated company address for each one 30 D.A. Clements, UW Information School5/26/2016

Databases are better No repetition Can search for exactly the data you need Solves the problem of information overload D.A. Clements, UW Information School 31 5/26/2016

Example List all students who received a "B" Spreadsheet 1. Sort the data 2. Scroll (and scroll) to find those in the "B" range Database 1. Query for students who received a "B" Results: All the students and only the students who received a "B" D.A. Clements, UW Information School 32 5/26/2016

Database Advantage You can Save a query for later Use over and over and over again Edit the query later Copy the query Format an attractive report that prints every time you run the query D.A. Clements, UW Information School 33 5/26/2016

The Database Disadvantage It takes time to set up the database and make sure it's working properly Spreadsheets are easier, faster to set up If they're small 5/26/2016D.A. Clements, UW Information School 34

How do you decide? Do changes made in one spreadsheet force you to make changes in another? Do you have several spreadsheets containing similar information (such as separate sheets with inventory for Dallas, D.C., and Detroit)? Do you want some data to be hidden from some users? 5/26/2016D.A. Clements, UW Information School 35

How do you decide? Can you see all pertinent data on one screen or do you have to keep scrolling? Are several people accessing the data at the same time? Do you have a hard time viewing the specific sets of data you want? Is the data you want divided among one or more spreadsheets? 5/26/2016D.A. Clements, UW Information School 36

Move to a database if… You answered "yes" to at least 2 of these questions 5/26/2016D.A. Clements, UW Information School 37

Next lecture… We'll continue to look at data storage, transfer, and retrieval Read Chapter 16 5/26/2016D.A. Clements, UW Information School 38